Season brisket all over with salt and crushed peppercorns. In a shallow dish, with a spoon, combine flour and garlic powder. Roll brisket in flour mixture to coat.
Heat oil in a large Dutch oven or stock pot over medium-high heat. Add brisket and cook for 5 minutes on each side, or until golden brown on all sides. Arrange carrots, potatoes, shallots, garlic, and rosemary around brisket. Pour wine over vegetables and cook for 1 minute. Add broth and bring to a simmer. Reduce heat to medium-low, cover and cook for 3 hours, until beef is tender. Remove brisket from pot and let stand for 10 minutes before slicing crosswise into thin slices.
Shred and reserve 2 cups beef for soft tacos, if desired.
Serve sliced beef with vegetables, shallots, garlic, and liquid from pot spooned over top.